1. Field of the Invention
The present invention relates to a magnet separator which separates and removes magnetic particles from a liquid to be processed.
2. Description of the Related Art
In machine processing, a large amount of coolant is used for cooling and lubrication. During processing, magnetic particles, such as chips and grinding dust, are mixed into the coolant. The mixed magnetic particles form sludge in the coolant. The coolant is repeatedly used by separating and removing the sludge after use.
Japanese Utility Model No. 3024673 discloses a magnet separator which captures sludge in a coolant, and discharges it. The separator comprises a cylindrical drum and a magnet provided inside of the cylindrical drum. The sludge is adsorbed onto an outer peripheral surface of the magnet drum by magnetic force of the magnet. The separator is provided with a squeeze roll which squeezes out a liquid contained in the sludge, and a scraper (sludge removal plate) which scrapes off the sludge out of which liquid has been squeezed from the outer peripheral surface of the drum.
The scraper described in the above-mentioned Japanese Utility Model No. 3024673 is pressed on the outer peripheral surface of the drum. Namely, a front end portion of the scraper is brought into intimate contact with the outer peripheral surface of the drum so as not to leave sludge adsorbed onto the outer peripheral surface of the drum.
When processing an oily coolant, an oil film is formed on the outer peripheral surface of the drum. When the amount of sludge is relatively large, the oil film is returned to a liquid storage part of a separator main body by an action of the squeeze roll. However, when machining is not performed, or when the amount of sludge is relatively small during machining, the oil film is not sufficiently removed by the action of the squeeze roll, and most of the oil film remains on the outer peripheral surface of the drum. The oil film is scraped off by the scraper, and flows into a sludge box. Accordingly, use of a scraper as described above causes loss of a liquid to be processed (i.e., a phenomenon in which the amount of a liquid to be processed decreases).
As measures to prevent the loss, enhancing the squeeze efficiency by, for example, increasing hardness of the squeeze roll or pressing the squeeze roll more hardly on the drum is considered. However, those measures require mechanical upgrading, which involves a substantial increase in costs. On the other hand, the measures produce only a limited effect, and are not drastic.